Many pressure, torque, vibration, and acceleration sensors which utilize the piezoresistive effect (i.e., the specific change of electrical resistivity with stress) are known. See, e.g., an article by Ahmed Amin entitled "Piezoresistivity in Semiconducting Ferroelectrics," appearing in "Disorder and Order in the Solid State", edited by Roger W. Pryor et al. (Plenum Publishing Company, 1988).
Some of the prior art piezoresistive sensors vary their resistivity with the application of stress. Thus, for example, some such sensors are fabricated on a precisely micromachined and etched n-type silicon wafer (diaphragm) whose optimum design is achieved by finite element techniques. See, for example, an article by A. Yasukawa et al. appearing in the Japanese Journal of Applied Physics, Volume 21, page 1049 (1982).
However, the prior art piezoresistive sensors whose resistivities vary with the application of stress do not show an appreciable response. Thus, the range of applications for these relatively crude sensors is limited.
It is an object of this invention to provide a piezoresistive sensor which exhibits a substantially greater change in its resistivity for a given change in applied stress than do prior art piezoresistive sensors.
It is yet another object of this invention to provide a process for fabricating the piezoresistive sensor of this invention.
It is yet another object of this invention to provide novel transducers comprised of the sensor of this invention.
It is yet another object of this invention to provide a novel process for the use of the piezoelectric sensor of this invention.